The compounds of formula I belong to a new class of chemical compounds which have the characteristic structure of 1,2-oxazole or isoxazole ##SPC3##
The synthesis of isoxazolic derivatives was thoroughly studied in the past and several methods for preparing the said compounds are known and described in the scientific literature [cf. e.g.: Ber., 28,2540 (1895); idem. 36, 3665 (1903); Compt. rend., 137, 795 (1903); J. Am. Chem. Soc., 49, 2078 (1927); Gazz. Chim. Ital., 70, 676 (1940); idem, 72, 99 (1942); idem, 76, 148 (1946)]. The methods described in the aforementioned references can be distinguished depending on whether they relate to: syntheses achieved by
Or
In accordance with this latter method an intermediate isoxazoline is obtained which, when subjected to an oxidation, e.g. by means of chromic acid, can be converted into the corresponding isoxazole derivative. This latter synthesis has however the disadvantage of yielding several by-products depending on the acidity of the reaction medium, the respective proportions of the reagents used and the nature of the substituents.